I am having one myself this weekend, so it seems apropos to read this short piece in The New York Times on the origin of the picnic:
The word “picnic,” however, is of more recent vintage. An early mention can be traced to a 1649 satirical French poem, which features the Frères Pique-nicques, known for visiting friends “armed with bottles and dishes.” In 1802, the term made a hop to Britain after a group of Francophiles in London formed a Pic-Nic Society to gorge, guzzle and perform amateur theatricals. Participants drew lots to determine who would supply which dish — from calf’s-foot jelly to blancmange.
Read the rest here.